[PATCH] firmware: cs_dsp: Remove redundant download buffer allocator

Richard Fitzgerald
2025-11-26T13:15:18Z

Now that cs_dsp uses regmap_raw_write() instead of regmap_raw_write_async()
it doesn't need to keep multiple DMA-safe buffers of every chunk of data
it wrote.

See commit fe08b7d5085a ("firmware: cs_dsp: Remove async regmap writes")

Only one write can be in progress at a time, so one DMA-safe buffer can be
re-used. The single DMA-safe buffer is reallocated if the next write chunk
is larger. Reallocation size is rounded up to reduce the amount of churn.
PAGE_SIZE is used as a convenient size multiple. Typically for .wmfw files
the first chunk is the largest.

A DMA-safe intermediate buffer is used because we can't assume that the
bus underlying regmap can accept non-DMA-safe buffers.

Note that a chunk from the firmware file cannot simply be split into
arbitrarily-sized chunks to avoid buffer reallocation. The data in the
firmware file is preformatted to be written directly to the device as one
block. It already takes account of alignment, write-bursts and write
length requirements of the target hardware, so that the cs_dsp driver can
treat it as an opaque blob.

Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>
---
drivers/firmware/cirrus/cs_dsp.c | 103 ++++++++++---------------------
1 file changed, 34 insertions(+), 69 deletions(-)

diff --git a/drivers/firmware/cirrus/cs_dsp.c b/drivers/firmware/cirrus/cs_dsp.c
index 36a5aefa16e7..6444ef1f7f32 100644
--- a/drivers/firmware/cirrus/cs_dsp.c
+++ b/drivers/firmware/cirrus/cs_dsp.c
@@ -13,6 +13,7 @@
#include <linux/ctype.h>
#include <linux/debugfs.h>
#include <linux/delay.h>
+#include <linux/math.h>
#include <linux/minmax.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
@@ -317,44 +318,6 @@ struct cs_dsp_alg_region_list_item {
struct cs_dsp_alg_region alg_region;
};

-struct cs_dsp_buf {
- struct list_head list;
- void *buf;
-};
-
-static struct cs_dsp_buf *cs_dsp_buf_alloc(const void *src, size_t len,
- struct list_head *list)
-{
- struct cs_dsp_buf *buf = kzalloc(sizeof(*buf), GFP_KERNEL);
-
- if (buf == NULL)
- return NULL;
-
- buf->buf = vmalloc(len);
- if (!buf->buf) {
- kfree(buf);
- return NULL;
- }
- memcpy(buf->buf, src, len);
-
- if (list)
- list_add_tail(&buf->list, list);
-
- return buf;
-}
-
-static void cs_dsp_buf_free(struct list_head *list)
-{
- while (!list_empty(list)) {
- struct cs_dsp_buf *buf = list_first_entry(list,
- struct cs_dsp_buf,
- list);
- list_del(&buf->list);
- vfree(buf->buf);
- kfree(buf);
- }
-}
-
/**
* cs_dsp_mem_region_name() - Return a name string for a memory type
* @type: the memory type to match
@@ -1481,7 +1444,9 @@ static int cs_dsp_load(struct cs_dsp *dsp, const struct firmware *firmware,
const struct wmfw_region *region;
const struct cs_dsp_region *mem;
const char *region_name;
- struct cs_dsp_buf *buf;
+ u8 *buf __free(kfree) = NULL;
+ size_t buf_len = 0;
+ size_t region_len;
unsigned int reg;
int regions = 0;
int ret, offset, type;
@@ -1601,23 +1566,23 @@ static int cs_dsp_load(struct cs_dsp *dsp, const struct firmware *firmware,
region_name);

if (reg) {
- buf = cs_dsp_buf_alloc(region->data,
- le32_to_cpu(region->len),
- &buf_list);
- if (!buf) {
- cs_dsp_err(dsp, "Out of memory\n");
- ret = -ENOMEM;
- goto out_fw;
+ region_len = le32_to_cpu(region->len);
+ if (region_len > buf_len) {
+ buf_len = round_up(region_len, PAGE_SIZE);
+ kfree(buf);
+ buf = kmalloc(buf_len, GFP_KERNEL | GFP_DMA);
+ if (!buf) {
+ ret = -ENOMEM;
+ goto out_fw;
+ }
}

- ret = regmap_raw_write(regmap, reg, buf->buf,
- le32_to_cpu(region->len));
+ memcpy(buf, region->data, region_len);
+ ret = regmap_raw_write(regmap, reg, buf, region_len);
if (ret != 0) {
cs_dsp_err(dsp,
- "%s.%d: Failed to write %d bytes at %d in %s: %d\n",
- file, regions,
- le32_to_cpu(region->len), offset,
- region_name, ret);
+ "%s.%d: Failed to write %zu bytes at %d in %s: %d\n",
+ file, regions, region_len, offset, region_name, ret);
goto out_fw;
}
}
@@ -1634,8 +1599,6 @@ static int cs_dsp_load(struct cs_dsp *dsp, const struct firmware *firmware,

ret = 0;
out_fw:
- cs_dsp_buf_free(&buf_list);
-
if (ret == -EOVERFLOW)
cs_dsp_err(dsp, "%s: file content overflows file data\n", file);

@@ -2167,7 +2130,9 @@ static int cs_dsp_load_coeff(struct cs_dsp *dsp, const struct firmware *firmware
struct cs_dsp_alg_region *alg_region;
const char *region_name;
int ret, pos, blocks, type, offset, reg, version;
- struct cs_dsp_buf *buf;
+ u8 *buf __free(kfree) = NULL;
+ size_t buf_len = 0;
+ size_t region_len;

if (!firmware)
return 0;
@@ -2309,20 +2274,22 @@ static int cs_dsp_load_coeff(struct cs_dsp *dsp, const struct firmware *firmware
}

if (reg) {
- buf = cs_dsp_buf_alloc(blk->data,
- le32_to_cpu(blk->len),
- &buf_list);
- if (!buf) {
- cs_dsp_err(dsp, "Out of memory\n");
- ret = -ENOMEM;
- goto out_fw;
+ region_len = le32_to_cpu(blk->len);
+ if (region_len > buf_len) {
+ buf_len = round_up(region_len, PAGE_SIZE);
+ kfree(buf);
+ buf = kmalloc(buf_len, GFP_KERNEL | GFP_DMA);
+ if (!buf) {
+ ret = -ENOMEM;
+ goto out_fw;
+ }
}

- cs_dsp_dbg(dsp, "%s.%d: Writing %d bytes at %x\n",
- file, blocks, le32_to_cpu(blk->len),
- reg);
- ret = regmap_raw_write(regmap, reg, buf->buf,
- le32_to_cpu(blk->len));
+ memcpy(buf, blk->data, region_len);
+
+ cs_dsp_dbg(dsp, "%s.%d: Writing %zu bytes at %x\n",
+ file, blocks, region_len, reg);
+ ret = regmap_raw_write(regmap, reg, buf, region_len);
if (ret != 0) {
cs_dsp_err(dsp,
"%s.%d: Failed to write to %x in %s: %d\n",
@@ -2342,8 +2309,6 @@ static int cs_dsp_load_coeff(struct cs_dsp *dsp, const struct firmware *firmware

ret = 0;
out_fw:
- cs_dsp_buf_free(&buf_list);
-
if (ret == -EOVERFLOW)
cs_dsp_err(dsp, "%s: file content overflows file data\n", file);

--
2.47.3